1. Field of the Invention
The present invention relates to a method of extruding a continuous profiled fastener onto a thermoplastic film substrate, and more particularly, pertains to a method for the continuous bonding of a profiled fastener assembly to a thermoplastic cuff film substrate through the intermediary of hot extrusion.
In various instances, during the production the of plastic bags which are provided with interengageably reclosable profiled fasteners thereon, it is desired to attach a profiled fastener to a cuff film which is arranged at the outside of the top of the plastic bag. In essence, a zipper-like thermoplastic profiled fastener is hot-extruded onto the substrate film material, and thereafter subjected to cooling so as to resultingly produce a permanent bond between the continuous profiled fastener and the substrate film material either prior to or concurrently with the formation of the plastic bag.
Quite frequently, the profiled fasteners, which are usually in the form of plastic zippers or interengageable male and female fastener elements, are produced by extruding the profiled fasteners in the form of continuous strip from an extrusion die so as to extend downwardly into a water bath; and thereafter drying and winding the strip-like profiled fastener onto spools for storage and subsequent use. When required for the formation of reclosable bags, strip-like profiled fasteners and a cuff film are respectively unwound from their separate storage spools, heat-sealed to each other, and then rewound in an assembly on another spool, or conveyed to a bag making machine. The heat sealing is implemented by either hot air, heated wheels or reciprocating hot-bar sealers, as is known in the technology.
Although all of the foregoing methods are essentially satisfactory in operation, they necessitate complex production procedures and apparatus, which frequently renders the manufacture of the bags laborious and uneconomical from the standpoint of mass-production costs.
2. Discussion of the Prior Art
Ausnit U.S. Pat. No. 3,532,571 provides for a method and an apparatus for the forming of plastic tubing incorporating separable pressure-responsive reclosable fastener strips employed in the production of plastic bags. The fasteners are extruded and then bonded to the film substrate by the continuous application of pressure and heat. This procedure, in effect, necessitates the slitting open of the tubular film and the subsequent forming into a bag. Although basically satisfactory in forming a zipper-like or reclosable fastener assembly on a plastic film substrate, the method and apparatus pursuant to this patent is extremely complex and resultingly expensive.
Yano U.S. Pat. No. 4,555,282 discloses a method and apparatus for bonding thermoplastic profiled fasteners to a film substrate, whereby the fasteners are hot extruded, thereafter applied onto the surface of the film under the action of a chill roll, subjected to a flow of air and thereafter immersed in a water bath. This is a relatively cumbersome procedure necessitating the implementation of a plurality of process steps which renders the entire method expensive when applied to the mass production of plastic bags.
Levy U.S. Pat. No. 3,917,890 discloses a method employed in the formation of a profiled fastener which is adhered to a tape and then conveyed through a cooling tank prior to being rolled into a spool or similar configuration.
Other methods and apparatus for producing composite profiled fastener and film substrate structures are described in Kamp U.S. Pat. No. 4,428,788; Yagi U.S. Pat. No. 4,259,133; Kamp U.S. Pat. 4,306,924 and Goto U.S. Pat. No. 3,462,332.
Although all of these publications are directed to various methods and apparatus of producing composite film and profiled fastener assembly, none of these facilitate the simple structure and method in hot-bonding profiled fasteners to a cuff film as contemplated by the present invention.
Other aspects of the prior art relate to separately extruding the two mating elements of zipper-like profiled fasteners; in effect, male and female, and then winding the extruded profiled fasteners onto separate spools, thereafter unwinding and feeding them as needed into position for bonding onto an advancing web of film employed for plastic bags. The profiled fastener is supported and guided by a grooved plate while a series of narrow heated wheels are adapted to be brought into contact with the film which is located over the profiled fastener, thereby heat sealing the film to the back of the profiled fastener structure. Alternatively, the profiled fastener and film may be backed up with a plate instead of the wheels.